Summary:
The Igor project is situated within the XXIB belt of Au-Ag epithermal deposits hosted in sedimentary rocks in northern Peru.
Field evidence suggests that the Igor project mineralization belongs to the epithermal type of gold-silver deposit.
The Igor project is centered on the informally named, northwest-striking, southeast-plunging Igor anticline, a major fold and topographic high that largely consists of the Chimú Formation quartz arenite in its core. Overlying the Chimú, and occurring on the limbs of the anticline, are a clastic sedimentary sequence of interlayered, lensing sandstone, siltstone, and thin black shale seams, which is assigned to the Santa and Carhuaz Formations.
A dacite porphyry stock (locally named the Huevo de Condor stock), and sills out crop within the southwestern limb of the anticline. Dacite porphyry dikes, thought to be emanating from the stock, occur within the northwest-trending anticlinal axis and within north- and northeast- trending structural zones cutting the anticline. The dacite intrusions are pre-mineralisation although there appears to be some spatial association with mineralization. It is likely that the same structural zones which were favorable for intrusive emplacement, were amenable to later hydrothermal fluid movement and subsequent mineralization. Minor granodiorite is present in some of the deep drillholes. The entire sequence has been cut by a variety of northwest-, northeast- and north-trending faults.
The crest of the Igor anticline is transected obliquely by the approximately north-south trending, near-vertical Callanquitas fault and vein system, that is at least 2.4 kilometers in length, and as much as 8.2 meters in width. It has been referred to as the "Callanquitas Structure" by Davis and Sim (2013) and consists of multiple fault splays, fault breccia and gouge, hydrothermal breccias, discontinuous narrow veins, vein breccias, stockworks, and brecciated porphyritic dacite dikes. Two major splays have been named "Callanquitas Oeste" and "Callanquitas Este". Because the individual Callanquitas mineralized zones have an over-all vein-like morphology, and gold-silver mineralization within it is not as wide as the entire host fault zone, for the purpose of reporting the mineralized zone, the author prefers the term "Callanquitas vein" when referring to the gold-silver deposit.
Mineralization
Igor project mineralization occurs within four primary target areas: Callanquitas, Domo, Tesoros, and Portachuelos. Mineralization within the property often occurs at the transition zone from Chimú up into the Santa and Carhuaz rocks. There is a spatial association of dacite porphyry dikes emplaced within structural breccias with both structural and manto-style mineralization.
The Igor project mineralization occurs within mineralized structural breccias that originally contained variable quantities of pyrite, arsenopyrite, and minor chalcopyrite. These sulfide minerals were subsequently strongly oxidized to significant depths.
Callanquitas Veins
The Callanquitas veins (Callanquitas Este, Callanquitas Oeste and Cianuro) occur within a north-south striking zone of multiple, anastomosing to divergent faults that extend over a length of 2,400 meters. Individual veins can be up to 1.5 km long with thicknesses between 0.2 to 8.2 meters. The Callanquitas structures are open along strike to the south and north, and at depth.
The Callanquitas mineralization is considered an intermediate-sulfidation type, consisting of mineralized structural breccias that originally contained variable quantities of pyrite, arsenopyrite, and minor chalcopyrite. These sulfide minerals were subsequently strongly oxidized to significant depths. The primary mineralized structures (Callanquitas Este and Oeste structures) are nearly vertical, but steep westerly dips are common.
The structures cut through a sequence of sandstone, siltstone, and quartzite. The silicified sandstone and quartzite units were more amenable to brecciation, and therefore more favorable for migrating hydrothermal fluids and mineralization. The dacite intrusive rocks are generally argillically-altered, and although the mineralized structures cut through the dacite, the general lack of brecciation and development of open-space renders the intrusions a poor host for mineralization.
Drilling indicates that mineralization in the Callanquitas Este and Oeste veins occurs over a 1,400 meters north-south strike length, and extends to depths of up to 500 meters below the topographic surface. Oxidation within the mineralized structures occurs to depths of 200 to 300 meters below surface. Ag/Au ratios are generally low (about 10:1) in the oxide portion of the deposit but can increase to over 100:1 at the oxide-sulfide interface. The change in Ag/Au ratios is not just related to supergene enrichment, but also represents the occurrence of late- stage, silver-rich, silica-sulfide veinlets which cut the more gold-rich hydrothermal breccias.
Domo
Domo mineralization occurs within a zone of bedded-parallel mantos and perpendicular veins along the crest of the southeast end of the Igor Anticline. Gold and silver mineralization is controlled by a series of northeast-southwest trending faults and occurs as oxidized pyritic breccias with variable silicification. The exploration program demonstrated that gold and silver mineralization are often present in mineable grades when a feeder system (vein, pebble dyke etc.) intersects the axial area of a significant anticlinal fold. This type of event resulted in mineralization in the Tesoros saddle reef / mantos. These tectonic conditions also resulted in mineralization at the Domo zone in the topographically highest area of the Igor Concession which is clearly evident in the extensive artisanal workings. Nine shallow (<50 meters) holes were drilled into this zone in 2007. Due to the friable nature of the manto material the first two drillholes, they did not have sufficient core recovery to be useful in making a resource estimate.
The Domo mineralized zone consists of five (5) NNE striking veins, three (3) of which can extend for 1.2 Km. Between 2006 and 2018, thirteen (13) diamond drillholes totalling 1907.78 meters were completed in the Domo zone. In the past, Hole DO-05 has intersected 12.6 g/t Au and 303.1 g/t Ag over 2.8 m.
Tesoros
Tesoros mineralization consists of gold and silver-bearing veins, breccias, and mantos along a major north-northeast striking fault that has localized the emplacement of dacitic porphyries and pebble Dykes.
The Tesoros fault/brecia zone contains an epithermal, high sulfidation mineralized deposit hosted in brecciated Chimu sandstones. The zone contains occurrences of high-grade mineralization. The previous drill program has shown that the breccia zone was cut off by the transverse fault and that the boiling zone of the hydrothermal fluids did not extend below the 3100-meter elevation.
Portachuelos
Portachuelos lies along the southern extension of the Callanquitas structural zone in an area where the north-south Callanquitas structure, and the northeast-trending Domo structures, and trend to the south and southwest into the western portion of the Huevo de Condor dacite porphyry stock. It is an early-stage exploration target.